Do I Need More RAM or an SSD?
If the computer is slow from the moment it starts up, an SSD makes the bigger difference. If it's fine at first but slows down once you've got several programs or browser tabs open, more RAM is the more likely fix.
Signs it's a storage problem
Slow startup, slow program loading, and general sluggishness from the moment the computer is turned on all point towards storage — particularly if the computer still has a mechanical hard drive.
Signs it's a memory problem
If the computer runs fine initially but bogs down as you open more programs, switch between apps, or accumulate browser tabs, that pattern points to memory rather than storage. Both can be checked properly during a diagnostic if you're not sure which applies.